2007 National Roadside Survey of Alcohol and Drug Use by Drivers

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2007 National Roadside Survey of Alcohol and Drug Use by Drivers: Drug Resultsoral fluid sample, and almost 50 percent of the drivers participating in the survey provided bloodsamples. The pilot study showed that it was clearly feasible to conduct a survey that includeddrugs other than alcohol. Such data are essential to developing more precise estimates of thepresence of alcohol and other drugs in drivers and for estimating the prevalence of alcohol- anddrug-involved driving.Prevalence of Drug-Involved DrivingIn their review of the research literature, Kelly, Darke, and Ross (2004) cite the 2001 NationalHousehold Survey to report that 4 percent of U.S. residents reported driving while under theinfluence of drugs in the preceding 12 months. These data, based on self-report, did notdistinguish between legal and illegal drugs. Using data collected in Tennessee in December1986, Lund, Preusser, Blomberg and Williams (1988) studied a sample of truck drivers to reportprevalence of marijuana (15%); cocaine (2%); prescription stimulants (5%); and nonprescriptionstimulants (12%) among the drivers. According to a literature review by Jones, Shinar, andWalsh (2003), the Lund et al. study (1988) was at that time the only U.S. study that hadperformed chemical tests of drivers stopped at a roadside location.With respect to prescription drugs, Jones et al. (2003) reported that benzodiazepines(tranquilizers) were found in four percent of non-crash-involved drivers. De Gier (2006)reviewed the literature and reported that benzodiazepines were more commonly found in middleagedto older drivers, “presumably due to the high rates of benzodiazepine prescriptions amongthese age groups.” Neutel (1998) estimated a lower crash risk for older persons (OR = 2.8) afterbenzodiazepine use than younger persons (OR = 3.2).Impact of Drugs on Driving SkillsLaboratory StudiesA number of laboratory studies have been conducted on the impact of both legal and illegaldrugs on driving-related skills. Still, results from these experimental studies are notstraightforward and are sometimes contradictory. One confounding factor is that different drugshave different effects on driving-related skills, with the thresholds at which those differenteffects occur varying as a function of the measure used (Shinar, 2006). Additionally, Shinarfound that because of the large individual variation in human response to drug consumption,attempts to define a “norm” for the behavioral response to drugs is difficult.Some studies have found that drugs that stimulate the central nervous system, (e.g.,amphetamines, cocaine, caffeine) sometimes may improve laboratory driving performance(Ward, Kelly, Foltin, & Fischman, 1997; Burns, 1993; Higgins et al., 1990; Hurst, 1976).However, in the Jones et al. (2003) literature review, it is reported that amphetamines are notusually associated with easily observable behavioral impairments.There is considerable evidence from laboratory studies that cannabis (marijuana) impairsreaction time, attention, tracking, hand-eye coordination, and concentration, although not all ofthese impairments were equally detected by all studies (Couper & Logan, 2004a; Heishman,Stitzer, & Yingling, 1989; Gieringer, 1988; Moskowitz, 1985). In reviewing the literature onmarijuana, Smiley (1998) concluded that marijuana impairs performance in divided attentiontasks (i.e., a poorer performance on subsidiary tasks). Jones et al. (2003) adds that Smiley’sfinding is relevant to the multitasking essence of driving, in particular by making marijuana-10
2007 National Roadside Survey of Alcohol and Drug Use by Drivers: Drug Resultsimpaired drivers perhaps less able to handle unexpected events. Interestingly, there is alsoevidence showing that, unlike alcohol, marijuana enhances rather than mitigates the individual’sperception of impairment (Lamers & Ramaekers, 1999; Robbe & O'Hanlon, 1993; Perez-Reyes,Hicks, Bumberry, Jeffcoat, & Cook, 1988). Robbe and O'Hanlon (1993) reported that inlaboratory conditions, drivers under the influence of marijuana were aware of their impairment,which led them to decrease speed, avoid passing other vehicles, and reduce other risk-takingbehaviors. Such was not the case with alcohol; for the authors reported that alcohol-impaireddrivers were generally not aware of impairment, and therefore did not adjust their drivingaccordingly.There is laboratory evidence that benzodiazepines impair some driving skills (Drummer, 2002).However, there are some contradictory results. Mathijssen et al. (2002) reported on a casecontrolstudy conducted in the Netherlands that found there is an increased risk forbenzodiazepine and alcohol use together, but no increased risk for benzodiazepine use alone.Additionally, there is evidence that the impairing effects of benzodiazepine might becircumscribed to the first days of benzodiazepine use, before tolerance develops (Lucki, Rickels,& Geller, 1985) leading some to conclude that the extent to which benzodiazepines increasecrash risk has to be balanced against the health benefits for those taking these drugs formedicinal purposes (Beirness, Simpson, & Williams, 2006).Laboratory reports are not necessarily the best indicators of the impact of drugs on driving skills.As Beirness et al. (2006, pages 16-17) stated: “an impairment or skill enhancement identified ina laboratory test may not show up on the road because the drugs may lead to other changes indriver behavior. Additionally, laboratory tests can address the effects of drugs only on skills, notjudgment, and the latter may be as important when it comes to driving. Thus even if drugs arefound to affect driving skills in laboratory tests, actual crash risk may or may not be affected.”Field DataData from drivers apprehended for impaired driving have been used to estimate the prevalence ofdrug use. Jones et al. (2003) reviewed the literature on drug involvement among arrested driversand reported a variety of drug prevalence levels based on the location and the population understudy. White et al. (1981) reported the following prevalence of drugs among drivers arrested forimpaired driving in California in the 1970s with BACs lower than .10 g/dL: sedative/hypnotic(30 to 47%); phencyclidine or PCP (79%); and morphine (62%). In contrast, Polkis, Maginn, andBarr (1987) reported the following prevalence rates among drivers arrested in St. Louis,Missouri, in the 1980s: phencyclidine or PCP (47%); marijuana (47%); benzodiazepines (22%);barbiturates (15%); opiates (11%); and cocaine (9%). Walsh et al. (2000) reported that marijuanaand cocaine were the primary drugs detected (19% and 16%, respectively) among arresteddrivers in Tampa, Florida, with narcotics and amphetamines found in less than 1 percent of thedrivers. Thus, as studies of drug-use patterns in the United States have shown, the types ofsubstances consumed vary across locations and time, making it difficult to characterize the druginvolvement of drivers.As part of the Drug Evaluation and Classification (DEC) Program, trained drug recognitionexperts are used to determine drug usage by looking for relevant signs and symptoms. Preusser,Ulmer, and Preusser (1992) evaluated DEC programs in Arizona, California, Colorado, NewYork, and Texas from 1986 to 1991 reported that about 1 to 3 percent of the drivers arrested fordriving while intoxicated (DWI) were classified as drug-impaired by Drug Recognition Experts11
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DOT HS 811 249December 2009
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2007 National Roadside Survey of Alcohol and Drug Use by Drivers

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